The dye laser is currently used as a source of laser excitation or amplification in applications of laser enrichment such as is shown, for example, in U.S. Pat. No. 3,944,947.
In such applications there are at least three principal objectives for the laser oscillator or amplifier, namely high energy in each laser pulse, high repetition rate, and an output beam of laser radiation of high optical quality, and low divergence. In these applications, output powers of several hundreds of watts at pulse rates of several hundreds of pulses per second in combination with an output beam as close to diffraction limited as possible are desired goals.
One of the important advances in laser systems in achieving these objectives has been the transverse pumped laser, as shown in U.S. Pat. No. 3,740,665 wherein the optical axis is transverse to the flow direction of the fluent laser material, or typically dye solution. This permits a rapid replenishment of expended dye into the region of the optical axis to increase both power and repetition rate. To some extent, both power and repetition rate can be augmented by respectively increasing the level of applied excitation to the optical axis and by increasing the flow velocity of the fluent laser material. Excessive heating, and breakdown in fluid dynamic flow characteristics are limiting factors here as well as turbulence effects which are augmented with flow velocity and excitation level due to uneven pressures and heating effects. In addition, the variation in refractive index throughout the fluent laser material produced by pressure and temperature variations greatly degrade the beam quality by contributing to random disorientations of the beam along the optical axis resulting in output beam divergence which may reach large magnitudes particularly at high repetition rates and excitation levels.